1. Field of the Invention
The present invention relates to a method to produce flexible ceramic thermal protection system (TPS) capable of surviving exposure to a high aeroacoustic noise level (170 decibel or greater) under fluctuating air loads, high temperature, and dynamic pressure conditions without the use or necessity of a surface coating to toughen the surface to the aeroacoustic load. The TPS is produced by having an integrally woven ceramic core structure filled with a ceramic insulation possessing high temperature stability and low thermal conductivity insulation properties.
2. Description of Related Art
Conventional ceramic insulation blankets are usually assembled in a sandwich-like construction in which a layer of ceramic insulation is placed between a single-ply top or face fabric and a bottom single-ply fabric and held together with a ceramic sewing thread in a quilted stitch pattern. Sewn blankets can use other ceramic fabrics besides silica. Another blanket configuration utilizes an integrally woven single-ply core structure filled with insulation. This thermal blanket is reported in the literature as Tailorable Advanced Blanket Insulation (TABI).
Disadvantages of Prior Art--The stitched blanket (held together with a sewing thread) can fail during exposure to fluctuating pressures and high aeroacoustic loads, e.g. 170 decibels and a dynamic pressure of 510 pounds per square foot (psf). This failure occurs after exposure to a radiant heat source as low as 10 minutes (min) at 1200.degree. F. In some cases, the thread or threads start breaking within one min and can propagate into fraying or tearing the surface fabric causing rapid destruction of the surface fabric followed by removal or loss of the insulation material. This loss renders the thermal insulation blanket useless for its intended purpose.
A single ply woven TABI, which utilizes an integral weave structure woven from 1800 denier silicon carbide yarn, when filled with silica batting will quickly show fabric fraying as well as movement of the insulation in the core or cell of the TABI structure. This occurs as low as 10 min at 1440.degree. F. exposure to a radiant heat source and similar sound pressure levels and dynamic pressures as the sewn, quilted blankets.
This destructive result limits both these thermal blankets to low aeroacoustic and low temperature applications thereby minimizing the advantage of flexible ceramic blankets for applications, particularly in situations where acoustic resistance is required without resorting to or requiring a surface ceramic coating to toughen the surface fabric. These coatings can also degrade or interact with the ceramic fabric when cured at or exposed to high temperatures. The coating also adds weight.
Some art of interest is:
S. R. Riccitiello, et al. in U.S. Pat. No. 4,713,275 disclose a rigid ceramic reusable externally applied thermal protection system.
A. R. Campman, et al. in U.S. Pat. No. 4,922,969 disclose a multilayer woven fabric having varying material composition through its thickness.
D. A. Kourtides, et al. in U.S. Pat. No. 5,038,693 disclose composite flexible multilayer insulation systems consisting of alternating layers of metal foil and ceramic scrim cloth or vacuum metallized polymeric films quilted together using a ceramic thread.
H. Goldstein et al., "improved Thermal Protection System for the Space Shuttle Orbiter." AIAA Paper 82-0630, May 1982.
B. Trujillo, et al., "In-Flight Load Testing of Advanced Shuttle Thermal Protection Systems." AIAA Paper 83-2704, November 1983.
P. M. Sawko, et al., "Effect of Processing Treatments of Strength of Silica Thread for Quilted Ceramic Insulation on Space Shuttle." SAMPE Quarterly, Vol. 6, No. 4, July 1985, pp. 17-12.
P. M. Sawko, et al., "Performance of Uncoated AFRSI Blankets during Multiple Space Shuttle Flights." NASA Technical Memorandum 103892, April, 1992.
D. Mui, et al., "Development of a Protective Ceramic Coating for Shuttle Orbiter Advanced Flexible Reusable Surface Insulation (AFRSI)." Ceramic Eng. and Sci. Proc., Vol. 6, No. 7-8, July-August 1985, pp. 793-805.
P. M. Sawko, "Flexible Thermal Protection Materials." NASA CP-2315, 1983, pp. 179-183.
P. M. Sawko, "Tailored Advanced Blanket Insulation (TABI)." NASA CP-3001, 1987, pp. 135-152.
D. P. Calamito, "Tailorable Advanced Blanket Insulation Using Aluminoborosilicate and Alumina Batting," Final Report. NASA CR-177527, July 1989.
C. F. Coe, "An Assessment of Wind Tunnel Test Data on Flexible Thermal Protection Materials and Results of New Fatigue Tests of Threads," Final Report. NASA CR 177466, April 1985.
C. F. Coe, "An Investigation of the Causes of Failure of Flexible Thermal Protection Materials in an Aerodynamic Environment," Final Report, NASA CR-166624, March 1987.
H. K. Larson, et al., "Space Shuttle Orbiter Thermal Protection Material Development and Testing," Proceedings of 4th Aerospace Testing Seminar, 1978, pp. 189-193.
P. M. Sawko, et al., "Development of a Silicon Carbide Sewing Thread." SAMPE Quarterly, Vol. 20, No. 4, July 1989, pp. 3-8.
P. M. Sawko, et al., "Strength and Flexibility Properties of Advanced Ceramic Fabrics." SAMPE Quarterly, Vol. 17, No. 1, October 1985.
H. K. Tran, et al., "Thermal Degradation Study of Silicon Carbide Threads Developed for Advanced Thermal Protection Systems." NASA Technical Memorandum 103952, August 1992.
None of these references individually or collectively teach or suggest the present invention.
All articles, publications, books, journals, patents and patent applications and the like are incorporated by reference in their entirety.
What is needed is an integrated design and identification of materials which produce a flexible ceramic thermal protection system which has improved mechanical, thermal and sonic properties to high aeroacoustic noise (i.e. preferably about 2000.degree. F., about 2300.degree. or 2400.degree. F. for 10 min, or 2500.degree. F. for 5 min). The present invention accomplishes these objectives.
Advantages of Invention of Prior Art
Some advantages over prior art include:
a. providing a ceramic blanket that can survive exposure to high aeroacoustic noise levels (170 decibels) after exposure to 2500.degree. F. radiant heat. PA1 b. providing a TPS that eliminates the need of a ceramic surface coating to improve the aeroacoustic performance of flexible ceramic TPS blankets after exposure to high temperatures. PA1 c. providing a low density TPS for a savings in weight. PA1 d. providing a flat, smooth surface for aerodynamic smoothness as compared to bumpy, quilted surface of sewn blankets. PA1 e. providing a multi-layer surface for integrally woven TPS articles without resorting to layering of stacking individual fabric layers. PA1 f. permitting the use of high temperature ceramic yarns such as silicon carbide to be used in a threadless fabrication method. PA1 a. using the TPS article to provide resistance to high aeroacoustic loads after exposure to a radiant heat environment. PA1 b. using a multi-layer weave construction such as angle interlock and layer-to-layer as a fabric surface capable of resisting high aeroacoustic noise levels. PA1 c. using the integration of multi-layer weave architecture as a face fabric of an integrally woven core structure. PA1 d. using the threadless (no sewing thread to assemble) method to fabricate high temperature high aeroacoustic noise capability TPS articles. PA1 a multilayer fabric surface for the top face fabric; PA1 a single layer fabric surface for the bottom face fabric surface; PA1 a single layer rib fabric which forms an angled truss configuration connecting the top face surface and bottom face surface; PA1 a high temperature stable ceramic insulation located between the top face and bottom face and adjacent to the surface of the rib truss fabric, PA1 (a) combining during weaving a multilayer top face sheet, a single layer bottom face sheet, and a rib fabric each woven of the same or different high temperature ceramic fiber (or tow) by simultaneous weaving and interconnection by the rib fabric at locations on the top face sheet and bottom face sheet which are designated as nodes; PA1 (b) warp fibers are woven in a plane at 90.degree. angle to the direction of the formed flutes and are filled parallel to the flutes which flutes define multiple three-dimensional triangular prism or trapezoidal prism open volumes; PA1 (c) filling the three-dimensional triangular prism or trapezoidal prism open volume with insulation comprising heat-resistant ceramic fibers; and PA1 (d) heat cleaning the formed structure at temperatures between about 800.degree. F. and 2000.degree. F., which expands the ceramic insulation of step (c) to fill the prism volume and PA1 (e) cooling the structure to ambient conditions. PA1 (a) obtaining multiple separate strands of a ceramic fiber or ceramic tow suitable for weaving; PA1 (b) utilizing a modified fly--shuttle loom or a rapier shuttleless loom, which is modified by adding nip rolls to the loom and modification of the fabric advancement mechanism, which loom has at least eight harnesses in conjunction with Dobby programming mechanism; PA1 (c) utilizing sufficient heddles for each warp fiber and a suitable reed which accommodates about 168 ends per in for a given fabric width wherein the top fabric has a shuttle, the rib fabric has a separate shuttle and the bottom fabric has a separate shuttle; PA1 (d) drawing fabric warp sheets into the loom through a series of tensioning bars and into each respective harness for each fabric; PA1 (e) utilizing an additional roller system to drive extra length rib fiber into the loom; PA1 (f) translating the warp and fill yarn sequencing in a Dobby pattern chain utilizing bar and by indicator wherein each bar represents one fill fiber insertion and each peg indicates the lifting of a specific harness; PA1 (g) weaving the fiber such that the Dobby mechanism reads one pattern bar instructing the loom to raise or lower one or more harnesses creating a shed opening; PA1 (h) conveying a shuttle through the shed opening dispensing a fill yarn into its proper location; PA1 (i) locking the fill yarn in place as the harness achieves its highest or lowest position which creates the next shed sequence, concurrently the reed pushes back the fill fiber into place and moves to its original back most position; PA1 (j) utilizing the same shuttle to traverse the created fabric in the opposite direction dispensing another fill yarn in the newly formed shed opening; PA1 (k) repeating steps (g), (h), (i) and (j) as needed to create the three dimensional angular open weave ceramic fabric structure described hereinabove.
The following features of this invention are novel: